GraphQL-core suffers from a validation rule called OverlappingFieldsCanBeMerged that, when processing nested inline fragments, performs repeated comparisons of fields sharing response names. This leads to quadratic or worst‑case O(n²·m²) CPU usage before any resolver or depth/complexity control runs, allowing an unauthenticated remote actor to lock a worker process with a short, highly compressible query and throttle the entire service. The flaw is a classic denial of service conditioned on client input, reflected in CWE-400, CWE-407, and CWE-770.

The affected product is GraphQL-core, the Python implementation of GraphQL.js. Versions from 3.0.0 through 3.2.11, and any pre‑release that predates the 3.2.12 fix, are vulnerable. This issue is fixed in versions 3.2.12 and 3.3.0rc1.

The CVSS score of 7.5 categorizes this as high severity. While the EPSS score is not available, the lack of authentication and the trivial nature of the exploit—submitting a small query—mean that the likelihood of exploitation is substantive for exposed services. The vulnerability is not listed in the CISA KEV catalog, yet any application that accepts GraphQL queries without additional safeguards is at risk of service interruption. The attack vector is remote, over the network, and does not require privileged access.